1. Field of the Invention
The present invention relates to a stable dispersion of a preformed polymer in a polyol and a process for preparation the same.
2. Description of Related Art
Polymer polyols, which are dispersions of a polymer in a polyol, are often included as a component in making reinforced polyurethane foam. For example, styrene/acrylonitrile (SAN) polymer polyols are common components in making reinforced polyurethane foam. SAN polymer polyols are dispersion polymerized, a process unfortunately requiring anywhere from about 6 to 24 hours. Furthermore, SAN polymer is more costly than alternative polymers such as polyethylene and polypropylene.
U.S. Pat. No. 4,014,846 (Ramlow et al.) discloses polymer polyols of hydroxy-containing polymer prepared by dispersing finely divided solid particles of a hydroxy-containing polymer in a polyol. Ramlow et al. describes polymerizing polymer particles in an organic solvent, isolating the particles and then dispersing the particles in a polyol. Preparing preformed polymer particles is process intensive, requiring the polymer particles to be prepared in an organic solvent and isolated prior to being dispersed into a polyol.
Accordingly, a stable dispersion of a relatively low-cost polymer in a polyol and a process for preparing such dispersions that is less capital and labor-intensive than described in prior art is desirable. Still more desirable is a process that is faster than the SAN dispersion polymerization process.
In a first aspect, the present invention is a process for making a stable dispersion comprising the steps: (a) contacting, in a single mixer, a preformed polymer resin and a polyol under conditions of sufficient heat and sufficient shear to form an initial dispersion of the polymer resin in the polyol; and (b) while under shear, cooling the initial dispersion sufficiently to form a stable dispersion.
In a second aspect, the present invention is a composition comprising a stable dispersion of a stabilizer and a preformed high-density or linear low-density polyethylene polymer in a polyol.
In a third aspect, the present invention is a polyurethane foam formulation comprising a dispersion of preformed polymer in polyol prepared according to the process of first aspect.
The present invention meets a need in the art by providing a stable dispersion of a relatively low-cost polymer in a polyol and a process for preparing such a stable dispersion that is less capital and labor intensive than described in prior art. Furthermore, the process of the present invention allows preparation of stable polymer in polyol dispersions in less than six hours.
Definitions
xe2x80x9cDispersionxe2x80x9d refers to a dispersion at the molecular or ionic level (a true solution) or colloidal level (having particle sizes up to hundreds of microns in diameter).
xe2x80x9cStable dispersionxe2x80x9d means stable to significant dispersed phase coalescence for at least a day, preferably at least a week, more preferably at least a month, still more preferably three months, even more preferably at least six months, most preferably at least a year.
xe2x80x9cStabilizerxe2x80x9d refers to an interfacially active compound that stabilizes a dispersion of a polymer in a polyol.
xe2x80x9cSingle mixerxe2x80x9d refers to a mixing device comprising one or more mixers that operate at identical mixing rates. Examples of single mixers include a beaker or tank in combination with one or more mixing blades on a single shaft and an extruder with multiple mixing elements all of which turn at the same rate. Examples of mixers which fall outside of the definition include combinations of extruders and dispersers wherein the screw(s) of the extruder operates at a different rate than the mixing head in the disperser (see for example, the extruder/disperser combination in pending U.S. patent application Ser. No. 60/35,086).